Аудиторный перевод

ISSUES ASSOCIATED WITH CONNECTION OF WIND FARMS TO WEAK AC NETWORKS

This article is intended to provide an overview of typical requirements imposed by regulatory authorities upon all generators, including power electronic based generation such as wind power generation. In light of these requirements, a number of issues associated with weak systems that impede wind generation from performing as required are presented, along with several examples of how these issues have impacted real wind interconnection projects.

Wind power plants (WPP) interconnected to high voltage transmission networks are expected to provide energy without negatively impacting the ability of transmission providers to serve their load in a safe, reliable, and cost effective fashion. In addition, they are increasingly expected to provide basic support functions which contribute to the overall good performance of the electric system. To ensure that wind plants and other equipment to be connected to power systems effectively support these two targets, network operators set performance requirements in their network connection codes (or "grid codes" or "connection requirements"). As network connection codes are an inherent part of the network planning criteria and practices, they may vary between synchronous areas and regions within synchronous areas, dependent also upon historical approaches that have been used as bases for robust network designs. Local phenomena affecting the transmission network performance (due to specific network topologies and generation characteristics, for example) may significantly affect the content of the network connection codes. Although connection codes may vary in specific details, on a more general level most codes address the following: 1) Frequency and voltage operation range; 2) Reactive power and voltage control; 3) Active power and frequency control; 4) Capability to ride through disturbances.

In addition to these main areas of technical performance requirements, connection codes typically address areas that are relevant for network planning and operation. For example, from a network planning perspective, essential areas include modelling requirements and requirements related to documentation of technical information.

One of the inherent challenges related to requirements set for WPPs is that they are subjected to technology development cycles which may be faster than the rate at which interconnection standards can be updated and applied. Issues related to connection points with relatively low short circuit capacity are a prime examples of grid connection related issues that may have been recognized in their full extent only late in the interconnection process, either at the stage of highly detailed grid connection studies or even after the power plant has been connected to network. In these cases interconnection standards may have been inadequate to predict the problems and correctly plan for the interconnection implementation procedures.

The following sections provide examples of the technical performance requirements that have been recognized to require special attention when the SCR at the connection point of the WPP is low. This is not a comprehensive list of grid code requirements, but a selection of issues impacted by weak systems.